Study of medium carbon air hardened bainitic cast steel

The microstructure, mechanical properties and wear resistance of medium carbon alloy steel have been investigated by means of the optical microscope, the scanning electron microscope, the tensile test, the hardness test, the impact test, the fracture test and the wear test. The results show that the bainite and retained austenite were obtained under the condition of air hardening in the carbon steel containing 0·30–0·45 wt-%C, by increasing the concentrations of silicon and manganese, adding proper boron, nickel, vanadium, titanium and rare earth, and appending the pretreatment of pearlitic anneal. The hardness, tensile strength, impact and fracture toughness of bainitic steel excelled 50 HRC, 1800 MPa, 30 J cm−2 and 70 MPa m1/2 respectively. It had excellent wear resistance under the two-body pin on disc wear and three-body impact wear. The serving period of hammer made of bainitic cast steel is 1·5–2·0 times longer than that of Hadfield austenitic steel.